Hmm, you just sort of lean in, and let nature take its course. Before you know it, you will want to do it again. I will tell you this though - Don't make an "event" out of it and announce "Ok, let's try to kiss now!". You will regret it later on. Just chill out. Be cool, then lean in and do it. Don't even talk about it. Don't even think about it. Just let it happen.
In case you need any suggestive hints as to what it should look like, this is pretty close:
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